git.oblomov.eu Git - git/blob - commit-graph.c

   1 #include "cache.h"
   2 #include "config.h"
   3 #include "dir.h"
   4 #include "git-compat-util.h"
   5 #include "lockfile.h"
   6 #include "pack.h"
   7 #include "packfile.h"
   8 #include "commit.h"
   9 #include "object.h"
  10 #include "revision.h"
  11 #include "sha1-lookup.h"
  12 #include "commit-graph.h"
  13
  14 #define GRAPH_SIGNATURE 0x43475048 /* "CGPH" */
  15 #define GRAPH_CHUNKID_OIDFANOUT 0x4f494446 /* "OIDF" */
  16 #define GRAPH_CHUNKID_OIDLOOKUP 0x4f49444c /* "OIDL" */
  17 #define GRAPH_CHUNKID_DATA 0x43444154 /* "CDAT" */
  18 #define GRAPH_CHUNKID_LARGEEDGES 0x45444745 /* "EDGE" */
  19
  20 #define GRAPH_DATA_WIDTH 36
  21
  22 #define GRAPH_VERSION_1 0x1
  23 #define GRAPH_VERSION GRAPH_VERSION_1
  24
  25 #define GRAPH_OID_VERSION_SHA1 1
  26 #define GRAPH_OID_LEN_SHA1 GIT_SHA1_RAWSZ
  27 #define GRAPH_OID_VERSION GRAPH_OID_VERSION_SHA1
  28 #define GRAPH_OID_LEN GRAPH_OID_LEN_SHA1
  29
  30 #define GRAPH_OCTOPUS_EDGES_NEEDED 0x80000000
  31 #define GRAPH_PARENT_MISSING 0x7fffffff
  32 #define GRAPH_EDGE_LAST_MASK 0x7fffffff
  33 #define GRAPH_PARENT_NONE 0x70000000
  34
  35 #define GRAPH_LAST_EDGE 0x80000000
  36
  37 #define GRAPH_FANOUT_SIZE (4 * 256)
  38 #define GRAPH_CHUNKLOOKUP_WIDTH 12
  39 #define GRAPH_MIN_SIZE (5 * GRAPH_CHUNKLOOKUP_WIDTH + GRAPH_FANOUT_SIZE + \
  40                         GRAPH_OID_LEN + 8)
  41
  42 char *get_commit_graph_filename(const char *obj_dir)
  43 {
  44         return xstrfmt("%s/info/commit-graph", obj_dir);
  45 }
  46
  47 static struct commit_graph *alloc_commit_graph(void)
  48 {
  49         struct commit_graph *g = xcalloc(1, sizeof(*g));
  50         g->graph_fd = -1;
  51
  52         return g;
  53 }
  54
  55 struct commit_graph *load_commit_graph_one(const char *graph_file)
  56 {
  57         void *graph_map;
  58         const unsigned char *data, *chunk_lookup;
  59         size_t graph_size;
  60         struct stat st;
  61         uint32_t i;
  62         struct commit_graph *graph;
  63         int fd = git_open(graph_file);
  64         uint64_t last_chunk_offset;
  65         uint32_t last_chunk_id;
  66         uint32_t graph_signature;
  67         unsigned char graph_version, hash_version;
  68
  69         if (fd < 0)
  70                 return NULL;
  71         if (fstat(fd, &st)) {
  72                 close(fd);
  73                 return NULL;
  74         }
  75         graph_size = xsize_t(st.st_size);
  76
  77         if (graph_size < GRAPH_MIN_SIZE) {
  78                 close(fd);
  79                 die("graph file %s is too small", graph_file);
  80         }
  81         graph_map = xmmap(NULL, graph_size, PROT_READ, MAP_PRIVATE, fd, 0);
  82         data = (const unsigned char *)graph_map;
  83
  84         graph_signature = get_be32(data);
  85         if (graph_signature != GRAPH_SIGNATURE) {
  86                 error("graph signature %X does not match signature %X",
  87                       graph_signature, GRAPH_SIGNATURE);
  88                 goto cleanup_fail;
  89         }
  90
  91         graph_version = *(unsigned char*)(data + 4);
  92         if (graph_version != GRAPH_VERSION) {
  93                 error("graph version %X does not match version %X",
  94                       graph_version, GRAPH_VERSION);
  95                 goto cleanup_fail;
  96         }
  97
  98         hash_version = *(unsigned char*)(data + 5);
  99         if (hash_version != GRAPH_OID_VERSION) {
 100                 error("hash version %X does not match version %X",
 101                       hash_version, GRAPH_OID_VERSION);
 102                 goto cleanup_fail;
 103         }
 104
 105         graph = alloc_commit_graph();
 106
 107         graph->hash_len = GRAPH_OID_LEN;
 108         graph->num_chunks = *(unsigned char*)(data + 6);
 109         graph->graph_fd = fd;
 110         graph->data = graph_map;
 111         graph->data_len = graph_size;
 112
 113         last_chunk_id = 0;
 114         last_chunk_offset = 8;
 115         chunk_lookup = data + 8;
 116         for (i = 0; i < graph->num_chunks; i++) {
 117                 uint32_t chunk_id = get_be32(chunk_lookup + 0);
 118                 uint64_t chunk_offset = get_be64(chunk_lookup + 4);
 119                 int chunk_repeated = 0;
 120
 121                 chunk_lookup += GRAPH_CHUNKLOOKUP_WIDTH;
 122
 123                 if (chunk_offset > graph_size - GIT_MAX_RAWSZ) {
 124                         error("improper chunk offset %08x%08x", (uint32_t)(chunk_offset >> 32),
 125                               (uint32_t)chunk_offset);
 126                         goto cleanup_fail;
 127                 }
 128
 129                 switch (chunk_id) {
 130                 case GRAPH_CHUNKID_OIDFANOUT:
 131                         if (graph->chunk_oid_fanout)
 132                                 chunk_repeated = 1;
 133                         else
 134                                 graph->chunk_oid_fanout = (uint32_t*)(data + chunk_offset);
 135                         break;
 136
 137                 case GRAPH_CHUNKID_OIDLOOKUP:
 138                         if (graph->chunk_oid_lookup)
 139                                 chunk_repeated = 1;
 140                         else
 141                                 graph->chunk_oid_lookup = data + chunk_offset;
 142                         break;
 143
 144                 case GRAPH_CHUNKID_DATA:
 145                         if (graph->chunk_commit_data)
 146                                 chunk_repeated = 1;
 147                         else
 148                                 graph->chunk_commit_data = data + chunk_offset;
 149                         break;
 150
 151                 case GRAPH_CHUNKID_LARGEEDGES:
 152                         if (graph->chunk_large_edges)
 153                                 chunk_repeated = 1;
 154                         else
 155                                 graph->chunk_large_edges = data + chunk_offset;
 156                         break;
 157                 }
 158
 159                 if (chunk_repeated) {
 160                         error("chunk id %08x appears multiple times", chunk_id);
 161                         goto cleanup_fail;
 162                 }
 163
 164                 if (last_chunk_id == GRAPH_CHUNKID_OIDLOOKUP)
 165                 {
 166                         graph->num_commits = (chunk_offset - last_chunk_offset)
 167                                              / graph->hash_len;
 168                 }
 169
 170                 last_chunk_id = chunk_id;
 171                 last_chunk_offset = chunk_offset;
 172         }
 173
 174         return graph;
 175
 176 cleanup_fail:
 177         munmap(graph_map, graph_size);
 178         close(fd);
 179         exit(1);
 180 }
 181
 182 /* global storage */
 183 static struct commit_graph *commit_graph = NULL;
 184
 185 static void prepare_commit_graph_one(const char *obj_dir)
 186 {
 187         char *graph_name;
 188
 189         if (commit_graph)
 190                 return;
 191
 192         graph_name = get_commit_graph_filename(obj_dir);
 193         commit_graph = load_commit_graph_one(graph_name);
 194
 195         FREE_AND_NULL(graph_name);
 196 }
 197
 198 static int prepare_commit_graph_run_once = 0;
 199 static void prepare_commit_graph(void)
 200 {
 201         struct alternate_object_database *alt;
 202         char *obj_dir;
 203
 204         if (prepare_commit_graph_run_once)
 205                 return;
 206         prepare_commit_graph_run_once = 1;
 207
 208         obj_dir = get_object_directory();
 209         prepare_commit_graph_one(obj_dir);
 210         prepare_alt_odb();
 211         for (alt = alt_odb_list; !commit_graph && alt; alt = alt->next)
 212                 prepare_commit_graph_one(alt->path);
 213 }
 214
 215 static void close_commit_graph(void)
 216 {
 217         if (!commit_graph)
 218                 return;
 219
 220         if (commit_graph->graph_fd >= 0) {
 221                 munmap((void *)commit_graph->data, commit_graph->data_len);
 222                 commit_graph->data = NULL;
 223                 close(commit_graph->graph_fd);
 224         }
 225
 226         FREE_AND_NULL(commit_graph);
 227 }
 228
 229 static int bsearch_graph(struct commit_graph *g, struct object_id *oid, uint32_t *pos)
 230 {
 231         return bsearch_hash(oid->hash, g->chunk_oid_fanout,
 232                             g->chunk_oid_lookup, g->hash_len, pos);
 233 }
 234
 235 static struct commit_list **insert_parent_or_die(struct commit_graph *g,
 236                                                  uint64_t pos,
 237                                                  struct commit_list **pptr)
 238 {
 239         struct commit *c;
 240         struct object_id oid;
 241         hashcpy(oid.hash, g->chunk_oid_lookup + g->hash_len * pos);
 242         c = lookup_commit(&oid);
 243         if (!c)
 244                 die("could not find commit %s", oid_to_hex(&oid));
 245         c->graph_pos = pos;
 246         return &commit_list_insert(c, pptr)->next;
 247 }
 248
 249 static void fill_commit_graph_info(struct commit *item, struct commit_graph *g, uint32_t pos)
 250 {
 251         const unsigned char *commit_data = g->chunk_commit_data + GRAPH_DATA_WIDTH * pos;
 252         item->graph_pos = pos;
 253         item->generation = get_be32(commit_data + g->hash_len + 8) >> 2;
 254 }
 255
 256 static int fill_commit_in_graph(struct commit *item, struct commit_graph *g, uint32_t pos)
 257 {
 258         uint32_t edge_value;
 259         uint32_t *parent_data_ptr;
 260         uint64_t date_low, date_high;
 261         struct commit_list **pptr;
 262         const unsigned char *commit_data = g->chunk_commit_data + (g->hash_len + 16) * pos;
 263
 264         item->object.parsed = 1;
 265         item->graph_pos = pos;
 266
 267         item->maybe_tree = NULL;
 268
 269         date_high = get_be32(commit_data + g->hash_len + 8) & 0x3;
 270         date_low = get_be32(commit_data + g->hash_len + 12);
 271         item->date = (timestamp_t)((date_high << 32) | date_low);
 272
 273         item->generation = get_be32(commit_data + g->hash_len + 8) >> 2;
 274
 275         pptr = &item->parents;
 276
 277         edge_value = get_be32(commit_data + g->hash_len);
 278         if (edge_value == GRAPH_PARENT_NONE)
 279                 return 1;
 280         pptr = insert_parent_or_die(g, edge_value, pptr);
 281
 282         edge_value = get_be32(commit_data + g->hash_len + 4);
 283         if (edge_value == GRAPH_PARENT_NONE)
 284                 return 1;
 285         if (!(edge_value & GRAPH_OCTOPUS_EDGES_NEEDED)) {
 286                 pptr = insert_parent_or_die(g, edge_value, pptr);
 287                 return 1;
 288         }
 289
 290         parent_data_ptr = (uint32_t*)(g->chunk_large_edges +
 291                           4 * (uint64_t)(edge_value & GRAPH_EDGE_LAST_MASK));
 292         do {
 293                 edge_value = get_be32(parent_data_ptr);
 294                 pptr = insert_parent_or_die(g,
 295                                             edge_value & GRAPH_EDGE_LAST_MASK,
 296                                             pptr);
 297                 parent_data_ptr++;
 298         } while (!(edge_value & GRAPH_LAST_EDGE));
 299
 300         return 1;
 301 }
 302
 303 static int find_commit_in_graph(struct commit *item, struct commit_graph *g, uint32_t *pos)
 304 {
 305         if (item->graph_pos != COMMIT_NOT_FROM_GRAPH) {
 306                 *pos = item->graph_pos;
 307                 return 1;
 308         } else {
 309                 return bsearch_graph(g, &(item->object.oid), pos);
 310         }
 311 }
 312
 313 int parse_commit_in_graph(struct commit *item)
 314 {
 315         uint32_t pos;
 316
 317         if (!core_commit_graph)
 318                 return 0;
 319         if (item->object.parsed)
 320                 return 1;
 321         prepare_commit_graph();
 322         if (commit_graph && find_commit_in_graph(item, commit_graph, &pos))
 323                 return fill_commit_in_graph(item, commit_graph, pos);
 324         return 0;
 325 }
 326
 327 void load_commit_graph_info(struct commit *item)
 328 {
 329         uint32_t pos;
 330         if (!core_commit_graph)
 331                 return;
 332         prepare_commit_graph();
 333         if (commit_graph && find_commit_in_graph(item, commit_graph, &pos))
 334                 fill_commit_graph_info(item, commit_graph, pos);
 335 }
 336
 337 static struct tree *load_tree_for_commit(struct commit_graph *g, struct commit *c)
 338 {
 339         struct object_id oid;
 340         const unsigned char *commit_data = g->chunk_commit_data +
 341                                            GRAPH_DATA_WIDTH * (c->graph_pos);
 342
 343         hashcpy(oid.hash, commit_data);
 344         c->maybe_tree = lookup_tree(&oid);
 345
 346         return c->maybe_tree;
 347 }
 348
 349 struct tree *get_commit_tree_in_graph(const struct commit *c)
 350 {
 351         if (c->maybe_tree)
 352                 return c->maybe_tree;
 353         if (c->graph_pos == COMMIT_NOT_FROM_GRAPH)
 354                 BUG("get_commit_tree_in_graph called from non-commit-graph commit");
 355
 356         return load_tree_for_commit(commit_graph, (struct commit *)c);
 357 }
 358
 359 static void write_graph_chunk_fanout(struct hashfile *f,
 360                                      struct commit **commits,
 361                                      int nr_commits)
 362 {
 363         int i, count = 0;
 364         struct commit **list = commits;
 365
 366         /*
 367          * Write the first-level table (the list is sorted,
 368          * but we use a 256-entry lookup to be able to avoid
 369          * having to do eight extra binary search iterations).
 370          */
 371         for (i = 0; i < 256; i++) {
 372                 while (count < nr_commits) {
 373                         if ((*list)->object.oid.hash[0] != i)
 374                                 break;
 375                         count++;
 376                         list++;
 377                 }
 378
 379                 hashwrite_be32(f, count);
 380         }
 381 }
 382
 383 static void write_graph_chunk_oids(struct hashfile *f, int hash_len,
 384                                    struct commit **commits, int nr_commits)
 385 {
 386         struct commit **list = commits;
 387         int count;
 388         for (count = 0; count < nr_commits; count++, list++)
 389                 hashwrite(f, (*list)->object.oid.hash, (int)hash_len);
 390 }
 391
 392 static const unsigned char *commit_to_sha1(size_t index, void *table)
 393 {
 394         struct commit **commits = table;
 395         return commits[index]->object.oid.hash;
 396 }
 397
 398 static void write_graph_chunk_data(struct hashfile *f, int hash_len,
 399                                    struct commit **commits, int nr_commits)
 400 {
 401         struct commit **list = commits;
 402         struct commit **last = commits + nr_commits;
 403         uint32_t num_extra_edges = 0;
 404
 405         while (list < last) {
 406                 struct commit_list *parent;
 407                 int edge_value;
 408                 uint32_t packedDate[2];
 409
 410                 parse_commit(*list);
 411                 hashwrite(f, get_commit_tree_oid(*list)->hash, hash_len);
 412
 413                 parent = (*list)->parents;
 414
 415                 if (!parent)
 416                         edge_value = GRAPH_PARENT_NONE;
 417                 else {
 418                         edge_value = sha1_pos(parent->item->object.oid.hash,
 419                                               commits,
 420                                               nr_commits,
 421                                               commit_to_sha1);
 422
 423                         if (edge_value < 0)
 424                                 edge_value = GRAPH_PARENT_MISSING;
 425                 }
 426
 427                 hashwrite_be32(f, edge_value);
 428
 429                 if (parent)
 430                         parent = parent->next;
 431
 432                 if (!parent)
 433                         edge_value = GRAPH_PARENT_NONE;
 434                 else if (parent->next)
 435                         edge_value = GRAPH_OCTOPUS_EDGES_NEEDED | num_extra_edges;
 436                 else {
 437                         edge_value = sha1_pos(parent->item->object.oid.hash,
 438                                               commits,
 439                                               nr_commits,
 440                                               commit_to_sha1);
 441                         if (edge_value < 0)
 442                                 edge_value = GRAPH_PARENT_MISSING;
 443                 }
 444
 445                 hashwrite_be32(f, edge_value);
 446
 447                 if (edge_value & GRAPH_OCTOPUS_EDGES_NEEDED) {
 448                         do {
 449                                 num_extra_edges++;
 450                                 parent = parent->next;
 451                         } while (parent);
 452                 }
 453
 454                 if (sizeof((*list)->date) > 4)
 455                         packedDate[0] = htonl(((*list)->date >> 32) & 0x3);
 456                 else
 457                         packedDate[0] = 0;
 458
 459                 packedDate[0] |= htonl((*list)->generation << 2);
 460
 461                 packedDate[1] = htonl((*list)->date);
 462                 hashwrite(f, packedDate, 8);
 463
 464                 list++;
 465         }
 466 }
 467
 468 static void write_graph_chunk_large_edges(struct hashfile *f,
 469                                           struct commit **commits,
 470                                           int nr_commits)
 471 {
 472         struct commit **list = commits;
 473         struct commit **last = commits + nr_commits;
 474         struct commit_list *parent;
 475
 476         while (list < last) {
 477                 int num_parents = 0;
 478                 for (parent = (*list)->parents; num_parents < 3 && parent;
 479                      parent = parent->next)
 480                         num_parents++;
 481
 482                 if (num_parents <= 2) {
 483                         list++;
 484                         continue;
 485                 }
 486
 487                 /* Since num_parents > 2, this initializer is safe. */
 488                 for (parent = (*list)->parents->next; parent; parent = parent->next) {
 489                         int edge_value = sha1_pos(parent->item->object.oid.hash,
 490                                                   commits,
 491                                                   nr_commits,
 492                                                   commit_to_sha1);
 493
 494                         if (edge_value < 0)
 495                                 edge_value = GRAPH_PARENT_MISSING;
 496                         else if (!parent->next)
 497                                 edge_value |= GRAPH_LAST_EDGE;
 498
 499                         hashwrite_be32(f, edge_value);
 500                 }
 501
 502                 list++;
 503         }
 504 }
 505
 506 static int commit_compare(const void *_a, const void *_b)
 507 {
 508         const struct object_id *a = (const struct object_id *)_a;
 509         const struct object_id *b = (const struct object_id *)_b;
 510         return oidcmp(a, b);
 511 }
 512
 513 struct packed_commit_list {
 514         struct commit **list;
 515         int nr;
 516         int alloc;
 517 };
 518
 519 struct packed_oid_list {
 520         struct object_id *list;
 521         int nr;
 522         int alloc;
 523 };
 524
 525 static int add_packed_commits(const struct object_id *oid,
 526                               struct packed_git *pack,
 527                               uint32_t pos,
 528                               void *data)
 529 {
 530         struct packed_oid_list *list = (struct packed_oid_list*)data;
 531         enum object_type type;
 532         off_t offset = nth_packed_object_offset(pack, pos);
 533         struct object_info oi = OBJECT_INFO_INIT;
 534
 535         oi.typep = &type;
 536         if (packed_object_info(pack, offset, &oi) < 0)
 537                 die("unable to get type of object %s", oid_to_hex(oid));
 538
 539         if (type != OBJ_COMMIT)
 540                 return 0;
 541
 542         ALLOC_GROW(list->list, list->nr + 1, list->alloc);
 543         oidcpy(&(list->list[list->nr]), oid);
 544         list->nr++;
 545
 546         return 0;
 547 }
 548
 549 static void add_missing_parents(struct packed_oid_list *oids, struct commit *commit)
 550 {
 551         struct commit_list *parent;
 552         for (parent = commit->parents; parent; parent = parent->next) {
 553                 if (!(parent->item->object.flags & UNINTERESTING)) {
 554                         ALLOC_GROW(oids->list, oids->nr + 1, oids->alloc);
 555                         oidcpy(&oids->list[oids->nr], &(parent->item->object.oid));
 556                         oids->nr++;
 557                         parent->item->object.flags |= UNINTERESTING;
 558                 }
 559         }
 560 }
 561
 562 static void close_reachable(struct packed_oid_list *oids)
 563 {
 564         int i;
 565         struct commit *commit;
 566
 567         for (i = 0; i < oids->nr; i++) {
 568                 commit = lookup_commit(&oids->list[i]);
 569                 if (commit)
 570                         commit->object.flags |= UNINTERESTING;
 571         }
 572
 573         /*
 574          * As this loop runs, oids->nr may grow, but not more
 575          * than the number of missing commits in the reachable
 576          * closure.
 577          */
 578         for (i = 0; i < oids->nr; i++) {
 579                 commit = lookup_commit(&oids->list[i]);
 580
 581                 if (commit && !parse_commit(commit))
 582                         add_missing_parents(oids, commit);
 583         }
 584
 585         for (i = 0; i < oids->nr; i++) {
 586                 commit = lookup_commit(&oids->list[i]);
 587
 588                 if (commit)
 589                         commit->object.flags &= ~UNINTERESTING;
 590         }
 591 }
 592
 593 static void compute_generation_numbers(struct packed_commit_list* commits)
 594 {
 595         int i;
 596         struct commit_list *list = NULL;
 597
 598         for (i = 0; i < commits->nr; i++) {
 599                 if (commits->list[i]->generation != GENERATION_NUMBER_INFINITY &&
 600                     commits->list[i]->generation != GENERATION_NUMBER_ZERO)
 601                         continue;
 602
 603                 commit_list_insert(commits->list[i], &list);
 604                 while (list) {
 605                         struct commit *current = list->item;
 606                         struct commit_list *parent;
 607                         int all_parents_computed = 1;
 608                         uint32_t max_generation = 0;
 609
 610                         for (parent = current->parents; parent; parent = parent->next) {
 611                                 if (parent->item->generation == GENERATION_NUMBER_INFINITY ||
 612                                     parent->item->generation == GENERATION_NUMBER_ZERO) {
 613                                         all_parents_computed = 0;
 614                                         commit_list_insert(parent->item, &list);
 615                                         break;
 616                                 } else if (parent->item->generation > max_generation) {
 617                                         max_generation = parent->item->generation;
 618                                 }
 619                         }
 620
 621                         if (all_parents_computed) {
 622                                 current->generation = max_generation + 1;
 623                                 pop_commit(&list);
 624
 625                                 if (current->generation > GENERATION_NUMBER_MAX)
 626                                         current->generation = GENERATION_NUMBER_MAX;
 627                         }
 628                 }
 629         }
 630 }
 631
 632 void write_commit_graph(const char *obj_dir,
 633                         const char **pack_indexes,
 634                         int nr_packs,
 635                         const char **commit_hex,
 636                         int nr_commits,
 637                         int append)
 638 {
 639         struct packed_oid_list oids;
 640         struct packed_commit_list commits;
 641         struct hashfile *f;
 642         uint32_t i, count_distinct = 0;
 643         char *graph_name;
 644         struct lock_file lk = LOCK_INIT;
 645         uint32_t chunk_ids[5];
 646         uint64_t chunk_offsets[5];
 647         int num_chunks;
 648         int num_extra_edges;
 649         struct commit_list *parent;
 650
 651         oids.nr = 0;
 652         oids.alloc = approximate_object_count() / 4;
 653
 654         if (append) {
 655                 prepare_commit_graph_one(obj_dir);
 656                 if (commit_graph)
 657                         oids.alloc += commit_graph->num_commits;
 658         }
 659
 660         if (oids.alloc < 1024)
 661                 oids.alloc = 1024;
 662         ALLOC_ARRAY(oids.list, oids.alloc);
 663
 664         if (append && commit_graph) {
 665                 for (i = 0; i < commit_graph->num_commits; i++) {
 666                         const unsigned char *hash = commit_graph->chunk_oid_lookup +
 667                                 commit_graph->hash_len * i;
 668                         hashcpy(oids.list[oids.nr++].hash, hash);
 669                 }
 670         }
 671
 672         if (pack_indexes) {
 673                 struct strbuf packname = STRBUF_INIT;
 674                 int dirlen;
 675                 strbuf_addf(&packname, "%s/pack/", obj_dir);
 676                 dirlen = packname.len;
 677                 for (i = 0; i < nr_packs; i++) {
 678                         struct packed_git *p;
 679                         strbuf_setlen(&packname, dirlen);
 680                         strbuf_addstr(&packname, pack_indexes[i]);
 681                         p = add_packed_git(packname.buf, packname.len, 1);
 682                         if (!p)
 683                                 die("error adding pack %s", packname.buf);
 684                         if (open_pack_index(p))
 685                                 die("error opening index for %s", packname.buf);
 686                         for_each_object_in_pack(p, add_packed_commits, &oids);
 687                         close_pack(p);
 688                 }
 689                 strbuf_release(&packname);
 690         }
 691
 692         if (commit_hex) {
 693                 for (i = 0; i < nr_commits; i++) {
 694                         const char *end;
 695                         struct object_id oid;
 696                         struct commit *result;
 697
 698                         if (commit_hex[i] && parse_oid_hex(commit_hex[i], &oid, &end))
 699                                 continue;
 700
 701                         result = lookup_commit_reference_gently(&oid, 1);
 702
 703                         if (result) {
 704                                 ALLOC_GROW(oids.list, oids.nr + 1, oids.alloc);
 705                                 oidcpy(&oids.list[oids.nr], &(result->object.oid));
 706                                 oids.nr++;
 707                         }
 708                 }
 709         }
 710
 711         if (!pack_indexes && !commit_hex)
 712                 for_each_packed_object(add_packed_commits, &oids, 0);
 713
 714         close_reachable(&oids);
 715
 716         QSORT(oids.list, oids.nr, commit_compare);
 717
 718         count_distinct = 1;
 719         for (i = 1; i < oids.nr; i++) {
 720                 if (oidcmp(&oids.list[i-1], &oids.list[i]))
 721                         count_distinct++;
 722         }
 723
 724         if (count_distinct >= GRAPH_PARENT_MISSING)
 725                 die(_("the commit graph format cannot write %d commits"), count_distinct);
 726
 727         commits.nr = 0;
 728         commits.alloc = count_distinct;
 729         ALLOC_ARRAY(commits.list, commits.alloc);
 730
 731         num_extra_edges = 0;
 732         for (i = 0; i < oids.nr; i++) {
 733                 int num_parents = 0;
 734                 if (i > 0 && !oidcmp(&oids.list[i-1], &oids.list[i]))
 735                         continue;
 736
 737                 commits.list[commits.nr] = lookup_commit(&oids.list[i]);
 738                 parse_commit(commits.list[commits.nr]);
 739
 740                 for (parent = commits.list[commits.nr]->parents;
 741                      parent; parent = parent->next)
 742                         num_parents++;
 743
 744                 if (num_parents > 2)
 745                         num_extra_edges += num_parents - 1;
 746
 747                 commits.nr++;
 748         }
 749         num_chunks = num_extra_edges ? 4 : 3;
 750
 751         if (commits.nr >= GRAPH_PARENT_MISSING)
 752                 die(_("too many commits to write graph"));
 753
 754         compute_generation_numbers(&commits);
 755
 756         graph_name = get_commit_graph_filename(obj_dir);
 757         if (safe_create_leading_directories(graph_name))
 758                 die_errno(_("unable to create leading directories of %s"),
 759                           graph_name);
 760
 761         hold_lock_file_for_update(&lk, graph_name, LOCK_DIE_ON_ERROR);
 762         f = hashfd(lk.tempfile->fd, lk.tempfile->filename.buf);
 763
 764         hashwrite_be32(f, GRAPH_SIGNATURE);
 765
 766         hashwrite_u8(f, GRAPH_VERSION);
 767         hashwrite_u8(f, GRAPH_OID_VERSION);
 768         hashwrite_u8(f, num_chunks);
 769         hashwrite_u8(f, 0); /* unused padding byte */
 770
 771         chunk_ids[0] = GRAPH_CHUNKID_OIDFANOUT;
 772         chunk_ids[1] = GRAPH_CHUNKID_OIDLOOKUP;
 773         chunk_ids[2] = GRAPH_CHUNKID_DATA;
 774         if (num_extra_edges)
 775                 chunk_ids[3] = GRAPH_CHUNKID_LARGEEDGES;
 776         else
 777                 chunk_ids[3] = 0;
 778         chunk_ids[4] = 0;
 779
 780         chunk_offsets[0] = 8 + (num_chunks + 1) * GRAPH_CHUNKLOOKUP_WIDTH;
 781         chunk_offsets[1] = chunk_offsets[0] + GRAPH_FANOUT_SIZE;
 782         chunk_offsets[2] = chunk_offsets[1] + GRAPH_OID_LEN * commits.nr;
 783         chunk_offsets[3] = chunk_offsets[2] + (GRAPH_OID_LEN + 16) * commits.nr;
 784         chunk_offsets[4] = chunk_offsets[3] + 4 * num_extra_edges;
 785
 786         for (i = 0; i <= num_chunks; i++) {
 787                 uint32_t chunk_write[3];
 788
 789                 chunk_write[0] = htonl(chunk_ids[i]);
 790                 chunk_write[1] = htonl(chunk_offsets[i] >> 32);
 791                 chunk_write[2] = htonl(chunk_offsets[i] & 0xffffffff);
 792                 hashwrite(f, chunk_write, 12);
 793         }
 794
 795         write_graph_chunk_fanout(f, commits.list, commits.nr);
 796         write_graph_chunk_oids(f, GRAPH_OID_LEN, commits.list, commits.nr);
 797         write_graph_chunk_data(f, GRAPH_OID_LEN, commits.list, commits.nr);
 798         write_graph_chunk_large_edges(f, commits.list, commits.nr);
 799
 800         close_commit_graph();
 801         finalize_hashfile(f, NULL, CSUM_HASH_IN_STREAM | CSUM_FSYNC);
 802         commit_lock_file(&lk);
 803
 804         free(oids.list);
 805         oids.alloc = 0;
 806         oids.nr = 0;
 807 }